The present embodiments relate to a multileaf collimator.
Multileaf collimators are used for focusing radiation beams in radiotherapy devices, for example, with the therapeutic application of X-rays. Absorption may be used to focus high-energy electromagnetic radiation or corpuscular radiation, for example, in tumor therapy. A multileaf collimator is introduced into a beam path of a corresponding radiation source. This multileaf collimator includes a plurality of leaves made of an absorbent material, for example, tungsten. The leaves may be displaced in relation to each other. The thickness of the leaves in the direction of the beams is matched to the radiation energy for the application in question due to the finite penetration depth of the radiation in the absorbent material. DE 196 39 861 A1 and WO 00/46813 disclose a multileaf collimator of this kind. The leaves are arranged in two opposing parcels or groups in parallel or in a slightly semicircular configuration. The leaves can be moved with their front faces toward each other and away from each other in a displacement direction defined by the position of the collimator lying substantially in a plane orthogonal to the direction of radiation. The respective leaves, with opposing front faces, may be moved in opposite directions into a closed position. It is possible to establish an aperture with any cross section, outside of which the radiation is absorbed by the leaves. To establish irregular cross-section shapes, DE 196 39 861 A1 discloses collimators with narrow leaves. The area to be irradiated for a therapeutic application may be established precisely using the leaves.
Exposure to radiation, for example, during therapeutic applications, should be precisely defined with respect to the area and the time of the exposure. Side effects, such as scatter and extended field radiation into regions not intended for exposure, for example, in edge zones, may be limiting factors. To minimize side effects, the geometry of the leaves at the edges of which radiation may be scattered and the precision of the adjusting mechanism for the leaves, the desired and actual positions of which must correspond to a sufficient degree, should be considered. The degree of absorption of the leaves is also important in minimizing side effects. A collimator, as described above, may have undesirable partial radiation transmission, which is known as leakage, for example, penetrability. The front faces of the leaves, when they are in closed position, may have leakage. For example, radiation components may pass between the front faces.